This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application entitled Method and Apparatus for Identifying A Bit Rate earlier filed in the Korean Industrial Property Office on the 18th day of January 1999, and there duly assigned Ser. No. 99-1264, a copy of which is annexed hereto.
1. Technical Field
The present invention relates to a method and apparatus for measuring the bit-rate of a received signal, and more particularly, to a method and apparatus for measuring the bit-rate of a received signal in a wavelength division multiplexing system.
2. Related Art
An optical fiber communication system consists of an information source, a transmitter or modulator, a transmission medium, and a receiver or demodulator at a destination point. The information source provides an electrical signal to the transmitter. The transmitter comprises an electrical stage which drives an optical source to give modulation of the light-wave carrier. The optical source which provides the electrical-optical conversion may be a semiconductor laser. The transmission medium consists of an optical fiber cable. The receiver consists of an optical detector which drives a further electrical stage and hence provides demodulation of the optical carrier. Thus there is a requirement for electrical interfacing at either end of the optical link. Fiber optic communications offer major advantages over wire systems because of low attenuation and high bandwidth available.
An optical fiber cable is an optical fiber waveguide having a core of a first refractive index n1 surrounded by a transparent cladding of slightly lower refractive index n2. The cladding supports the waveguide structure while also substantially reducing radiation loss into surrounding air. The optical fiber cable corresponds to a single cylindrical glass fiber having a diameter comparable to the diameter of a human hair. The optical fiber cable acts as an open optical waveguide. Light which is launched into an optical fiber at an angle less than an acceptance angle demonstrate total internal reflection in the core of the optical fiber. Periodic structures may be incorporated into planar waveguides to form integrated optical filters. An optical filter can be used to guide light to the core of an optical fiber causing the light to propagate in the core of that optical fiber.
Time division multiplexing (TDM) is a form of multiplexing in which different individual message signals are input to a multiplexer, are sampled periodically in order to create one group of interleaved pulses, and then the one group of interleaved pulses are output from the multiplexer. Then, the one group of interleaved pulses are transmitted along a single data transmission channel. In other words, the different individual message signals are combined to form a single signal. The single signal can have a much higher bit rate for transmission than any one of the different individual message signals. The group of interleaved pulses, also known as a train of pulses, is analyzed at the destination end of the single data transmission channel in order to recreate the original different individual message signals. Usually the data signals comprising the characters of each message are grouped as units of short duration, which are transmitted along with framing bits providing information for the transmission and receiving equipment. When using the time division multiplexing technique, the contents of the different individual message signals occupy the same transmission channel but during different moments in time.
Wavelength division multiplexing (WDM) is a form of multiplexing in which different individual message signals are input to a multiplexer, are combined, and then are output from the multiplexer. Then, the combined signals having different wavelengths are transmitted along a single data transmission channel such as a single optical fiber. Thus, components combine signals at several different wavelengths, the combined signals are transmitted through an optical fiber to a demultiplexer. There is minimal interference and minimal interaction among the signals while being transmitted along the optical fiber. The demultiplexer then splits them apart and routes them to their different destinations. Wavelength division multiplexing is becoming more important because it can multiply the transmission capacity of a single fiber without the installation of new cable.
I have found that optical communication systems can be inefficient and inconvenient, and I have found that there is a need for improved components related to wavelength division multiplexing systems.
To solve the aforementioned inefficiency and inconvenience, it is an objective of the present invention to provide a method for identifying the bit-rate of a received signal in a wavelength division multiplexing (WDM).
It is a further objective of the present invention to provide an apparatus for identifying the bit-rate of a received signal in a wavelength division multiplexing (WDM).
Accordingly, to achieve the above objectives and others, there is provided a method for identifying a bit-rate of a signal received in a wavelength division multiplexing system. The method includes the steps of delaying the received signal and comparing the delayed received signal with the original received signal based on a time slot to generate a selection signal, and extracting the bit-rate of the received signal by measuring a voltage level of the selection signal, such as a direct current (DC) voltage. The received signal can be considered to be an original signal.
The selection signal generating step includes the steps of duplicating the received signal to output two signals which are the same as the received signal, delaying one of the two same signals by a predetermined time, and performing an exclusive OR logic operation on a delayed signal and the other signal which is not delayed among the two same signals, to generate the selection signal. The delay step includes the steps of establishing a maximum bit-rate for measurement, calculating a 1-signal hold time corresponding to the established maximum bit-rate, and determining the delay time by multiplying the 1-signal hold time by a predetermined value.
The step of extracting the bit-rate includes the steps of filtering the selection signal, measuring the direct current voltage level of the filtered signal and determining the bit-rate of the received signal according to a range corresponding to the measured voltage level, and analog-to digital (A/D) converting the filtered signal.
There is also provided an apparatus for identifying a bit-rate of a signal received in a wavelength division multiplexing (WDM) system. Such an apparatus can be referred to as an identification unit. The apparatus includes a selection signal generator for delaying the received signal and comparing the delayed received signal with the original received signal based on a time slot to generate a selection signal, and a bit-rate extracting unit for determining the bit-rate of the received signal from a direct current voltage level of the selection signal. The received signal can be a data signal.
The selection signal generator includes a buffer for duplicating the received signal to output two signals which are the same as the received signal, a delay unit for receiving one of the two same signals and delaying that one signal by a predetermined time, and an operation unit. The operation unit receives the other one of the two same signals, which is directly transmitted from the buffer without delay, and also receives the delayed signal from the delay unit. The operation unit performs an exclusive OR logic operation on the two received signals to generate a bit-rate selection signal. The bit-rate extracting unit includes a filter for filtering the selection signal, and a determination unit for determining the bit-rate of the received signal from the direct current voltage level of the filtered signal.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a method, comprising: receiving an original signal; delaying a first signal to generate a delayed signal, said first signal corresponding to said original signal; comparing said delayed signal with said original signal, and generating a selection signal in dependence upon said comparing; and identifying a bit-rate of said original signal by measuring a direct current voltage level of said selection signal.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an apparatus, comprising: a signal generator receiving an original signal, delaying a first signal to generate a delayed signal, said first signal corresponding to said original signal, and comparing said original signal with said delayed signal based on a time slot to generate a selection signal; and a bit-rate extracting unit receiving said selection signal and determining a bit-rate of said original signal in dependence upon a direct current voltage level of said selection signal.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides a method for identifying a bit-rate of an original signal received in a wavelength division multiplexing transfer, the method comprising the steps of: receiving an original signal, delaying said original signal, comparing said delayed original signal with said original signal based on a time slot, generating a selection signal in dependence upon said comparing; and extracting a bit-rate of said original signal by measuring a voltage level of said selection signal.
To achieve these and other objects in accordance with the principles of the present invention, as embodied and broadly described, the present invention provides an apparatus for identifying a bit-rate of a signal received in a wavelength division multiplexing transfer, the apparatus comprising: a selection signal generator delaying an original signal to generate a delayed signal, comparing said original signal with said delayed signal based on a time slot to generate a selection signal; and a bit-rate extracting unit determining a bit-rate of said original signal from a voltage level of said selection signal.
The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example. Other advantages and features will become apparent from the following description and from the claims.